A five-foot-tall man could use a bow with a six-foot-long stave any day of the week, if he had the strength and skill to draw it. Just the curve of a bow usually lops the thing by about 5% to 10% of its length, and the center is held at shoulder-height. In theory, a five-foot-tall man could use a bow with an eight-foot-long stave.
As for STR requirements... The Heavy Crossbow requires a mechanical winch to reload, in PnP.
As for Dwarves getting Exotic for Dwarven Waraxes, they really should. Just edit the requirements to include Dwarves, like Rapiers include Elves. They SHOULD do that, already.